High intensity focused ultrasound (HIFU) is an exciting new therapeutic technology with numerous significant potential clinical benefits. This technique involves delivering high levels of energy (e.g., 2000 watts/ cm2) to a region of tissue and elevating its temperature to 60 - 80 degrees C within seconds. The effect is similar to the way a magnifying glass focuses sunrays onto a piece of paper to burn it. This ultrasound action can ablate tumors, pre-coagulate a region of an organ to be surgically resected and obtain hemostasis in hemorrhaging parenchyma and vessels. Further, regions of tissue can be treated that are not only on the organ surface but deep within the organ itself, without appreciable exposure or harm to the intervening tissue. Specifically, the researchers at the University of Washington have demonstrated the potential of HIFU in achieving rapid hemostasis in vivo, using models of organ and blood vessel injuries. Herein, a research team of bioengineers and surgeons proposes to further develop, refine and clinically test HIFU methodology for the operating room. Traumatic liver and spleen injury are the focus because they are common injuries with high morbidity and mortality, where conventional therapies have limited efficacy. Plans are made to a) investigate HIFU hemostasis mechanisms, b) engineer practical surgical devices, c) optimize the devices, d) refine and test them in pre-clinical, in vivo hemorrhage models, e) clinically test them in liver and spleen trauma, and f) finally conduct clinical assessment in reducing trauma mortality and morbidity. Two surgical problem areas will be investigated: 1) when the bleeding site is visible to the surgeon and 2) when blood or investing tissue hide it. Thus, two hemostasis device styles will be developed. The first will be simple probes for HIFU application when the bleeding region is visible. The second will be more complicated and include simultaneous ultrasound detection methods for locating the bleeding site and electronic focusing for guiding HIFU to the bleeding regions. The investigators believe these devices will promote significantly improved and cost effective methods for stopping bleeding in the injured liver and spleen. The devices will facilitate accelerated hemostasis, reduced blood loss, increase splenic salvage, shorten surgical time, avoid damage control surgery and attendant secondary repair, and finally improve hemodynamics in patients with multiple injuries. Thus, the investigators believe that their proposed studies will result in a new and clinically applicable methodology for reducing mortality and morbidity in abnormal trauma.